Human granulocytic ehrlichiosis (HGE) is an emerging tick-borne disease caused by an obligate intracellular bacterium in the genogroup Ehrlichia phagocytophila (EP). Human EP infections range from inapparent to fatal. Serodiagnosis, usually by IFA, is problematic due to cross reactivity with other infectious agents, interference by autoantibodies, and interlaboratory variability. Moreover, EP culture and purification required for production of this and other test platforms are inefficient and hazardous. To circumvent these difficulties, a dot EIA with EP recombinant antigens will be developed to provide a commercial test which is rapid, easily performed, and sensitive and specific. Two recombinant EP-specific antigens, Msp (the immunodominant but variable EP protein) and AnkA (a conserved EP protein) will be evaluated in a quantitative dot EIA dipstick format. Sensitivity and specificity will be determined with each antigen separately and combined, using IFA and Western blotting as reference methods. Archived sera employed will be from confirmed HGE cases, nonimmune individuals, other disease states including other ehrlichioses, and retrospective serosurveys. The results also will be used to assess the recombinant antigen production and purification methods. This feasibility study should provide a basis for the manufacture of prototype dot EIA kits and extensive field testing in Phase II. PROPOSED COMMERCIAL APPLICATION: HGE is sometimes fatal, emerging disease whowe true incidence and geographic range are unknown. Identification of HGE cases would be enhanced by a reliable diagnostic test that can be performed in clinical settings. A sensitive and specific dot EIA test based on recombinant antigens would overcome many of the shortcomings of the currently available diagnostic methods. PanBio InDx already distributes ehrlichial and rickettsial test kits worldwide, and the ehrlichial market is expected to expand.